1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device, and more particularly, to a method for protecting the bottom of an opening against processing in a subsequent step in the formation of a capacitor or in a dual Damascene process.
2. Background Art
For protecting the bottom of an opening, a method has been conventionally adopted wherein where a cylindrical capacitor of a semiconductor is, for example, formed, an opening is formed in an oxide film, after which a film, such as polysilicon, is formed over the whole surface and an organic film, such as a resist, is formed by a coating method and exposure is effected so that the resist film is left as an etching mask only at the bottom of the opening, thereby protecting the polysilicon film, followed by etching back to remove the region other than the polysilicon inside the opening (e.g., see Japanese Patent Laid-open No. Hei 8-204150 (page 4, FIG. 1)).
In the conventional method of protecting the bottom of an opening of a semiconductor device, a positive photoresist is used for an organic film employed as a protecting material and is subjected to whole surface exposure to completely remove the resist from the upper portion of the opening through exposure and development. Because exposure light does not arrive at the bottom of the opening, the resist is left thereat, which is used to realize the protection of the polysilicon film at the bottom of the opening. Similar effects are obtained using, for another method, a method wherein an organic film, such as a resist, is applied and subsequently etched back.
However, these methods have the problems that if the resist at the bottom of the opening is left where aspect ratio of the opening is small, i.e., where the depth of the opening is small or area of the opening is large, the resist on the upper portion of an insulating film around the opening may also be left, or the resist at the bottom of the opening may be undesirably removed if the resist on the upper portion of the insulating film is removed.